Duplication with heat-meltable solvent for hectographic coloring material



Apnl 30, 1963 D. A. NEWMAN 3,088,028

DUPLICATION WITH HEAT-MELTABLE SOLVENT FOR HECTOGRAPHIC COLORINGMATERIAL Filed June 1'7, 1960 INVENTOR. Douy Z as A. New/775m MRONLQUnited States Patent DUPLICATION WITH HEAT-MELTABLE SOLVENT FORHECTOGRAPHIC COLORING MATERIAL Douglas A. Newman, Glen Cove, N.Y.,assignor to Columbia Ribbon and Carbon Manufacturing Co., Inc.,

Glen Cove, N.Y., a corporation of New York Filed June 17, 1960, Ser. No.36,951 6 Claims. (Cl. 250-65) This invention relates to the process ofimaging copy sheets having thereon normally solid coatings comprisingheat-meltable material which in its melted form is a solvent forhectograph coloring material by means of heat.

Heretofore hectograph copies have been made by reproduction processeswhich have been carried out by systerns generally referred to in the artas either the gelatin system or as the spirit duplicating system. In thegelatin system, a master sheet is imaged by typing, writing or otherwiseinscribing with an ink composition including a water-soluble dye. Thisimage is then transferred in reverse from the master by absorptionduring contact against a gelatin layer. The water-soluble dyestulf isthen transferred from the moist gelatin layer to a superpositioned copysheet impressed on the imaged gelatin printing medium.

In prior known spirit duplicating systems, the image is formed on themaster by transfer from a carbon type sheet coated with a compositioncontaining a high proportion of a spirit-soluble or waterandspirit-soluble dye. The image on the master is then partially dissolvedand transferred from the master to successive copy sheets, the surfacesof the copy sheets having been wetted with an alcohol or an alcohol andWater fluid. This image reproduction on the copy sheet is effected bycontacting the fluid dampened surface of the copy sheet with the imagedsurface of the master sheet while processing the thus assembled sheetsbetween the compression cylinders of a rotary duplicating machine. Inthis spirit duplicating system, the image is formed on the mastergenerally in mirror reverse, in order to produce a direct reading copywhen reproduced on the copy sheet.

These known hectograph processes have numerous disadvantages which maketheir use impractical where it is desired to produce only a few copies.For instance, since the master sheet must be imaged manually, it is justas simple to type the desired copies in duplicate rather than employ thehectograph duplicating process.

It is an object of this invention to avoid these and other shortcomingsof the prior known spirit duplicating systems, and this is accomplishedby providing a dry hectograph printing process.

It is another object of this invention to provide for the imaging ofnovel copy sheets with a hectograph dye transfer sheet through the useof infrared radiation in the absence of any hectograph master sheet andin the absence of the usual spirit duplicating fluids.

It is another object of the present invention to provide for the imagingof novel copy sheets by complementary chemical reagents-through the useof infrared radiation and in the absence of imaging pressures.

It is a still further object of the present invention to provide for theautomatic imaging of a copy sheet directly corresponding to an imagedoriginal sheet and in the absence of combustible volatile solvents.

These and other objects are accomplished in the manners hereinafterdescribed.

The most important feature of the present invention is the novel methodof preparing duplicate copies of an original sheet without the necessityof first preparing a 'hectograph master sheet, and without the necessityof 3,%8,02$ Patented Apr. 30, 1963 53 employing solvents as required bythe known spirit duplicating processes.

Other features and advantages will hereinafter appear.

In the accompanying drawing:

FIGURE 1 is a fragmentary sectional view showing an original sheet, atransfer sheet bearing a layer containing coloring matter, and a copysheet bearing a layer of heat fusible solvent material, said sheetsbeing superposed under the influence of radiation but being shown out ofcontact for purposes of clarifying the illustration.

FIG. 2 is a fragmentary sectional view of the transfer and copy sheetsof FIG. 1 after irradiation and separation of the sheets, demonstratingthe imaged areas on the copy sheet and the affected portions of thetransfer sheet.

As illustrated by the drawings, the present invention is concerned witha method of selectively activating certain portions of a heat-fusiblesolvent layer 31 of a copy sheet 30 so that only those portions whichare fused and melted function as active solvents for a color donor layer21 of a transfer sheet 20 in contact therewith. The selective activationis accomplished through the use of infrared radiation 50 and an originalsheet 10 bearing images 11 comprising infrared radiation-absorbingmaterial.

In this manner, when infrared radiation is applied against the originalit is absorbed by the images thereon and converted to heat. This heatpattern, corresponding to the images on the original sheet, penetratesto the copy sheet, the coating of which becomes melted in the heatedareas. The coating on the copy sheet, in its melted liquid state, is asolvent for the coloring matter of the transfer sheet and therebydissolves this coloring matter from the transfer sheet in areascorresponding to the imaged areas of the original sheet to form a truecopy thereof. This procedure may be repeated as many times as necessary,using the same transfer sheet, to produce as many copies as may bedesired. It should be made clear at this point that the order of sheetsshown in the drawing may be changed where desired. For instance, if anoriginal sheet is to be duplicated but it has imaging on both sides,then it is preferred to place such original sheet on the bottom underthe copy sheet with the surface to be duplicated facing the copy sheet.Also in some instances where it is desired to have a convenientself-duplicating transfer sheet which may be copied from time to time,then the original sheet may be omitted and the infraredradiation-absorbing images may be present on the transfer sheet on theside opposite the color-forming layer.

The present invention involves the use of a copy paper free of imagingpigment or dyestuff comprising a paper sheet coated on its printing sidewith a heat modifiable, heat softenable or a low melting point solid,which when heated softens and becomes variously otherwise modified intoa state in which it is a solvent for the coloring material used on thetransfer sheet. Any one of a number of fusible solids such as the solidalcohols, fatty acids or esters may be employed for the coating on thecopy paper, the essential requirement being that when they areheatactivated they are solvents for the coloring material on thetransfer sheet. Examples of materials which may be used are solidalcohols such as cetyl, myristyl and stearyl; solid fatty acids such asstearic, palmitic, lauric and capric; solid esters of various glycolsand of organic acids; and solid glycol ethers such as the polyethyleneand polypropylene-glycol ethers. By the term coating as used herein ismeant a superficial film of heat-modifiable solid material, the majorpart of which impregnates the paper foundation and is held below thesurface thereof. Such coating is applied in an amount just sufficient towet the surface of the copy sheets and insufiicient to result in theformation of a separate frangible layer on the surface of the sheet. -Itis important to the present process that the coating on the copy sheetsbe non-transferable to the transfer sheet under the effects of heat orpressure in that such transfer would frustrate any attempt to image thecopy sheets and would also result in contamination and destruction ofthe transfer sheet.

The non-transferability of the copy sheet coatings of the presentinvention is effected by controlling the amount of heat-modifiable solidmaterial which is applied to the paper foundation. As will be understoodby those skilled in the art, various grades of paper have differentdegrees of absorbency. Thus a heavy coating may be applied to roughpaper stock and will be absorbed thereby while the same amount ofcoating will form a pressure-transferable layer if applied to high gradeor sized paper. The surface of any paper sheet, under magnification, istoothy and shows the presence of fibers, rough spots, interstices andhigh and low spots. As indicated supra, the degree of roughness dependsupon the type and quality of the paper and whether it is sized orotherwise treated. If one Wishes to apply a pressure-transfer layer to apaper foundation, it is well-recognized that a certain amount of thetransfer material is lost or wasted due to impregnation by the papersheet and saturation of the surface rough spots and interstices. Suchimpregnation and saturation is necessary to provide tooth for thetransfer coating but, however, the amount of material used up for thesepurposes is firmly held by the foundation sheet and is not transferableunder pressure. Only that amount of the coating, beyond that held byinterfacial attraction, is pressure-transferable.

According to the present invention, only that amount of coating materialis applied which is necessary to fill the surface interstices and to wetthe fibers and form a very thin but continuous film on the paperfoundation. Such film is substantially non-transferable in that it isfirmly attached to the surface fibers and rough spots. In other Words, agiven amount of coating must be consumed in Wetting and filling thesurface inconsistencies of a paper sheet and it is that amount which isworkable for producing copies in the present heat process. Just enoughmaterial is applied so that there is no transfer to and contamination ofthe master sheet, but enough material is applied to afford a continuousdeveloping layer on the surface of the paper foundation.

It is also important that the coating on the copy sheets softens andmelts at a temperature within the range of approximately 90 to about 150F. which is the temperature range of the present process. Lower meltingcoatings tend to tackify at room temperatures causing sticking of thestored copy sheets, while coatings having melting temperatures in excessof about 150 F. are exceedingly hard and resist melting and preventimaging of the copy sheets.

Besides the above-mentioned fusible or otherwise modified solids, stillother compositions may be used for coat ing a copy sheet. Thus acomposition including a low melting wax which in itself is not a dyesolvent for the dye in the master image but which Wax includes admixedtherewith a substantial amount of a dye solvent may be used as such acopy sheet coating. Then when the copy sheet and the film forming thecoating thereon is heated above atmospheric or room temperature, thecomposition softens. The solubility of the said composition in itssoftened and modified state will then be effective to dissolvesufiicient coloring matter from the imaged master to form a legiblecopy. An example of such a coating can be prepared by mixing togetherequal parts by weight of a wax such as microcrystalline wax or beeswaxand a liquid solvent or developer such as oleic acid. octadecyl alcoholor ethylene glycol, melting the 4 mixture and coating it on a sheet ofcopy paper to form such a film.

When the duplication is to be effected, the normally and comparativelysolid (at room temperature) coating on the copy sheet is modified orsoftened and if necessary even melted by a suitable infrared radiationsource such as infrared lamp bank 50 and the modified coating becomes asolvent for the coloring matter present on the transfer sheet. Thus bysubjecting the original sheet, the copy sheet and its immediatelycontigmous transfer sheet to infrared radiation and sufiicient pressureto maintain intimate contact therebetween, the contact of the normallysolid but now selectively modified solvent on the copying surface of thecopy sheet with the layer on the surface of the transfer sheetcontaining coloring matter dissolves some of the coloring matter fromthe transfer layer to reproduce the desired copy.

The source of infrared radiation is not critical although the use of aninfrared radiation lamp is generally preferred, particularly whenincorporated in a convenient apparatus such as the Thermofax machine orconventional fiat-bed apparatus. The length of exposure time, of course,depends upon the strength and proximity of the radiation source but, ingeneral, exposure is continued only long enough to provide for a heatgeneration in the imaged areas of the original sheet sufficiently ,highto melt the solvent layer on the copy sheet in the corresponding areas,generally between about two and ten seconds. Thus temperatures withinthe range of about F. to about 200 F. are preferred.

According to the present invention, the layer on the transfer sheetcomprises a conventional hectograph dyestufi, preferably carried by asuitable binder such as wax or ethyl cellulose, the dyestuff being onewhich absorbs substantially no infrared radiation. Suitable dyestuffsinclude conventional hectograph dyestuffs from the triarylmethane,safranine and rhodamine families. It should be understood, however, thatthe transfer layer does not transfer bodily to the copy sheet in thepresent process, due mainly to the fact that the melted surface on thecopy sheet is not receptive to the transfer layer. Secondly, theradiation necessary to melt the copy sheet coating is generally muchless than that necessary to melt the transfer layer of a hectographtransfer sheet. Although conventional hectograph transfer sheets may beemployed in the present process, it should be understood that muchthinner dye layers may be used, with or without a wax binder. Also,other known resinous binders may be substituted for the wax such as thecellulosic resins and the vinyl resins. It is generally preferred,though not necessary, that the binder for the dyestuff also be at leastpartly soluble in the melted solvent of the copy sheet.

Also, substantially colorless conventional complementary chemical colorformers may be employed in place of hectograph dyestuffs. For instance,the transfer sheet may contain one color-forming chemical such as anorganic acid, such as gallic or tannic acid; a thiocyanate derivativesuch as the potassium, ammonium or sodium salts, trimethyl thiocyanateor tolyl thiocyanate; or a sodium, potassium or ammonium salt offerrocyanide or ferricyanide; etc., While the heat-fusible copy sheetcontains the corresponding chemical which when brought into liquidcontact with the chemical of the master sheet reacts therewith to form asharp colored image on the copy sheet. The corresponding chemical on thecopy sheets may be an iron salt such as ferric chloride, ferric ammoniumsulfate or iron benzoate, etc.; a copper salt such as cupric chloride,copper acetate or cupric potassium sulfate, etc.; and the correspondingsalts of manganese, lead, silver, mercury, nickel and others well knownto the art. In this embodiment, the heat-fusible solid material on thecopy sheets liquefies under heat and appears to function in a twofoldmanner. In the first place, it melts in areas corresponding to theimaged areas of the original sheet and absorbs and dissolves some of thechemical from the transfer master sheet in these areas; secondly, itserves as a liquid reaction medium for the complementary chemicalreagents, namely the chemical originally present on the copy sheets andthe chemical dissolved and absorbed from the transfer sheet, therebycausing the chemicals to react and form a sharp colored copycorresponding to the imaged areas of the original sheet. To aid in thereaction it is preferred to have a hum'ectant present on the copysheets, which absorbs humidity and renders the chemicals more completelyionically available for reaction. Materials such as ethylene glycol andthe Carbowaxes function particularly well as humectants.

Other variations using complementary chemical reagents may be employed.For instance both chemicals may be present on either the fusible copysheet or the transfer sheet in substantially colorless unreacted form.The corresponding transfer or fusible copy sheet is provided with anacidic or alkaline catalyst which, when contacted in liquid form withthe chemical reagents on the corresponding sheet, causes them to reactand form colored images in the preselected areas corresponding to theimaged areas of the original sheet.

The fused, melted or otherwise heat modified coating almost immediatelyafter forming the duplicate copy from the master sheet solidifies orreturns to its normal and comparatively solid state and readilyseparates from its contiguous transfer sheet.

In preparing the copy sheets of this invention, one of the preferredcoatings of the heat modifiable or nieltable kind for the copy sheetshas a plasticizing agent included therei-n.- Such a coating whensubjected to heat causes the solvent to ooze out over [the coatedsurface.- A specific example of such a coating mixture would be made upof equal parts by Weight of dibutyl phthalate and cetyl alcohol coatedon the surface or impregnated into the copy sheet web. When subjected toheat the solvent migrates to the surface and when contacted with thetransfer sheet produces a legible copy by dissolving and absorbingcoloring matter therefrom.

After being subjected to sutficient radiation and sufficient pressure tomaintain intimate contact between the original, transfer and copysheets, the completed copy cools down to room temperature, and the heatmodified portions of the coating on the copy sheet almost immedi atelyreturn to their original unmodified state to produce a copy of theimaged original sheet. Thereafter other copy sheets can be continuouslyprocessed in a similar manner using the same transfer sheet until thedesired number of copies is produced.

The copy sheet of this invention may be made by several diverse methods.For example, the normally solid and heat modifiable solvent may bemelted and coated on the web of paper from which the copy sheets aremade by hot rolling methods. Alternatively, some of the normally solidand heat modifiable solvent materials, such as the solid alcohols, maybe dissolved in suitable volatile solvents and applied to the copy paperby any one of a number of conventional coating methods such as hot melt,emulsion coatings, spraying solvent coatings, dusting and fusingcoatings or other means. Thus, for example, by blending granules of thenormally solid meltable solvent and dispersing the resultant finegranular materials in a water emulsion and coating the emulsion onto thecopy paper, evaporation of the aqueous vehicle leaves a coating suitablefor carrying out the process of this invention. The amount of coatingapplied is generally quite small and only sufficient to wet the surfaceof the copy sheets. Upon setting or drying, the coating is nearlyentirely absorbed by the copy sheets which become impregnated in thismanner. The use of an excess amount of coating material is to be avoidedin that it remains on the copy sheet surface as a frangible,transferable layer which tends to become mushy during use andcontaminate the transfer sheet.

A number of coating compositions embodying heat modifiable or meltablematerial-s may be coated onto the copy sheet 30. These coatings are suchas fuse, otherwise modify or may even become liquid in areas subjectedto the increased temperature of the process of this invention and inthis modified or fused, or even liquid state, have the necessary dye orchemical solvency to' reproduce record data" on the surface of copysheets where selectively heated by infrared lamps while in contact witha dyeor chemical-containing transfer sheet.

The following examples of coating mixtures suitable for use on the copysheet are merely illustrative and not to be understood as limitativeembodiments:

Example 11 (Molten state coating) Carbowax 4000' (solid polyethyleneglycol polymer having an average molecular weight between 3000 and 3700)70.0 Colloidal clay 30.0

100.0 Example III (Water dlspersihle binder) Water 100.0 Carboxymethylcellulose (medium viscosity) 3.0 Carbowax 4000"; 10.0

113.0 Example IV (Emulsion type) Stearic acid 12.0 Oleic acid 12.0Triethanolamine 1.2 Hot 'Wat6l 165.0

190.2 Example V (Solvent type) Rosin (wood rosin) 12.0 Tricresylphosphate 3.0 Ethyl acetate 80.0 Colloidal clay 5.0

100.0 Example VI (Molten state coating) Carbowax 4000 50.0 Colloidalclay 20.0 Copper sulfate a 30.0

From the above examples, it is to be noted that several types ofcoatingscan be used to produce the copy sheets. in Examples I, II and VIabove, the fusible material itself is hot rollcoated or knife coated andabsorbed in the molten state by the surface of a web of paper from whichthe copy sheets are formed. In still another example, a suitablemeltable solid dissolved in a volatile solvent is coated on the copysheet and evaporation of the volatile solvent results in a heatmodifiable film containing the sglvent for the chemical or dye beingabsorbed by the copy s eet. r

In Examples III and IV, the solid material is held as dispersedparticles in a fluid film former such as casein, carboxymethylcellulose, starch, polyvinyl alcohol or any water-dispersible colloidsuch as is commonly used in the paper industry. In the latter case, thesolid material is preferably present in discrete particulate form, theparticles of which fuse and melt together when subjected to heat asherein described to effect impregnation of the copy sheets andreproduction in accordance with the disclosure herein made.

In Example V, a natural rosin or synthetic resin of similar propertiesmodified with a suitable plasticizer such as castor oil or tricresylphosphate or the like is dissolved in a suitable solvent such as ethylacetate and coated on a copy sheet. The evaporation of the solventleaves the absorbed film having the desirable properties of thisinvention.

Example VI shows the use of a copper sulfate on the copy sheet. Itshould be understood that any of the aforementioned copy sheetcomplementary chemical reagents may be substituted in place thereof,preferably in an amount ranging from about 20-40% by weight, based uponthe total Weight of the coating composition.

Variations and modifications may be made within the scope of the claimsand portions of the improvements may be used without others.

This application is a continuation-in-part of application Serial No.791,770, filed February 6, 1959, now abandoned, and application SerialNo. 9,049, filed February 16, 1960.

I claim:

1. The process of preparing duplicate copies of imaged subject mattercontaining infrared radiation-absorbing material which comprisessuperposing said imaged subject matter together with a transfer sheethaving a layer comprising color-forming material and a copy sheet havinga normally solid coating thereon comprising heat-meltable materialwhich, in its melted form, is a solvent for the color-forming materialof the transfer sheet, and subjecting the superposed sheets to infraredradiation for a period of time sufiicient to cause the solid coating ofthe copy sheet to melt in areas corresponding to said imaged subjectmatter and thereby dissolve and absorb colorforming material from thelayer of the transfer sheet to produce a duplicate copy of said imagedsubject matter.

2. The process of preparing duplicate copies of an imaged original sheetby means of infrared radiation which comprises superposing the originalsheet bearing images containing infrared radiation-absorbing material, atransfer sheet having a layer comprising hectograph dyestuff, and a copysheet having a solid coating thereon comprising heat-meltable materialwhich, in its melted form, is a solvent for the dyestufif of thetransfer sheet, and subjecting the superposed sheets to infraredradiation for a period of time sufiicient to cause the solid coating ofthe copy sheet to melt in areas corresponding to the imaged areas of theoriginal sheet and thereby dissolve and absorb dyestuif from thetransfer sheet to produce a duplicate copy of said original sheet.

3. The process of preparing duplicate copies of an imaged original sheetby means of infrared radiation which comprises superposing the originalsheet bearing images containing infrared radiation-absorbing material, atransfer sheet having a layer comprising a substantially colorlesscolor-forming chemical compound, and a copy sheet having a normallysolid coating thereon comprising heatmeltable material which, in itsmelted form, is a solvent for the chemical compound of the transfersheet, and which contains a different substantially colorless chemicalcompound which is reactive with said color-forming chemical compoundupon contact to form a colored reaction product, and subjecting thesuperposed sheets of infrared radiation for a period of time sufiicientto cause the solid coating of the copy sheet to melt in areascorresponding to the imaged areas of the original sheet and therebydissolve and absorb said color-forming chemical compound from thetransfer sheet to produce a duplicate copy of said original sheet.

4. The process of preparing duplicate copies of an imaged original sheetby means of infrared radiation which comprises superposing the originalsheet bearing images containing infrared radiation-absorbing material, atransfer sheet having a layer comprising hectograph dyestuff, and a copysheet having a solid coating thereon comprising a heat-meltable materialselected from the group consisting of alcohols, fatty acids, esters andethers which, in its melted form, is a solvent for the dyestufi of thetransfer sheet, and subjecting the superposed sheets to infraredradiation for a period of time sufiicient to cause the solid coating ofthe copy sheet to melt in areas corresponding to the imaged areas of theoriginal sheet and thereby dissolve and absorb dyestufi from thetransfer sheet to produce a duplicate copy of said original sheet.

5. The process of preparing duplicate copies of imaged subject mattercontaining infrared radiation-absorbing material which comprisessuperposing said imaged subject matter together with a transfer sheethaving a layer comprising a first color-forming chemical compoundselected from the group consisting of gallic acids, thiocyanates,ferrocyanides and ferricyanides and a copy sheet having a normally solidcoating thereon comprising a heat-meltable material which, in its meltedform, is a solvent for the color-forming chemical compound of thetransfer sheet and contains a second chemical compound which is reactivewith said first chemical compound and is selected from the groupconsisting of salts of iron, copper, manganese, lead, silver, mercuryand nickel, and subjecting the superposed sheets to infrared radiationfor a period of time sufiicient to cause the solid coating of the copysheet to melt in areas corresponding to said imaged subject matter andthereby dissolve and absorb said first color-forming chemical compoundfrom the layer of the transfer sheet to react with said second chemicalcompound on the copy sheet to produce a duplicate copy of said imagedsubject matter.

6. The process of imaging a copy sheet having a normally solid coatingthereon comprising heat-meltable material which, in its melted form, isa solvent for hectograph coloring material, which process comprisessuperposing said copy sheet with a second sheet having thereonhectograph coloring material, the coating on the copy sheet being insurface contact with said hectograph coloring material, and applyingheat for a period of time sufficient to cause the solid coating of thecopy sheet to melt and thereby dissolve and absorb said hectographcoloring material from said second sheet to produce a duplicate copythereof on said copy sheet.

References Cited in the file of this patent UNITED STATES PATENTS Re.24,554 Clark et a1. Oct. 21, 1958 2,769,391 Roshkind Nov. 6, 19562,813,042 Gordon et al Nov. 12, 1957 2,868,124 Crawford Jan. 13, 19592,910,377 Owen Oct. 27, 1959 2,939,009 Tien May 31, 1960 2,954,311Vander Weel Sept. 27, 1960

1. THE PROCESS OF PREPARING DUPLICATE COPIES OF IMAGED SUBJECT MATTERCONTAINING INFRARED RADIATION-ABSORBING MATERIAL WHICH COMPRISESSUPERPOSING SAID IMAGED SUBJECT MATTER TOGETHER WITH A TRANSFER SHEETHAVING A LAYER COMPRISING COLOR-FORMING MATERIAL AND A COPY SHEET HAVINGA NORMALLY SOLID COATING THEREON COMPRISING HEAT-MELTABLE MATERIALWHICH, IN ITS MELTED FORM, IS A SOLVENT FOR THE COLOR-FORMING MATERIALOF THE TRANSFER SHEET, AND SUBJECTING THE SUPERPOSED SHEETS TO INFRAREDRADIATION FOR A PERIOD OF TIME SUFFICIENT TO CAUSE THE SOLID COATING OFTHE COPY SHEET TO MELT IN AREAS CORRESPONDING TO SAID IMAGED SUBJECTMATTER AND THEREBY DISSOLVE AND ABSORB COLORFORMING MATERIAL FROM THELAYER OF THE TRANSFER SHEET TO PRODUCE A DUPLICATE COPY OF SAID IMAGEDSUBJECT MATTER.